Radiofrequency unit



Dec. 25, 1928.

1,696,675 T. E. FRIEND RADIO FREQUENCY UNIT Filed Jan. 24, 1927 lmmmmmmz //VVEN 70/? 77/500025 E Pie/5N0 Patented Dec. 25, 1928.

UNITED STATES THEODORE E. 111mm), OF NORWALK, OHIO.

BADIOFREQUEN CY UNIT.

Application filed January 24, 1927. Serial No. 162,983.

My invention relates to radio apparatus and particularly to improvements 1n radio frequency units. The purpose of the invention is to improve devices of this character 5 in such a manner as to obtain the maximum of amplification.

The annexed drawing and the following description set forth in detail certain means embodying my invention, such disclosed means. however. comprising but one of the various forms in' which the principle of the invention may be employed.

In said annexed drawing the figure is a diagrammatic arrangement of conventional radio apparatus in which my improved frequency unit has been incorporated.

Referring to the annexed drawing, I designate an in-put radio-frequency tube by the ordinal 1, an out-put tube by the ordinal 2,

a variable condenser bv the ordinal 3, my

improved frequency unit or coil by the ordinal 4, and a B battery by the ordinal 5. The variable condenser 3 is a conventional type having the stator plates 6 insulated from the frame 7 by the insulating bushings 8, and the rotor plates 9 meshing with the stator plates 6-to form the variable capacity.

The connections of the circuit are similar to most circuits for an intermediate stage of radio frequency, the primary winding 24 of the improved coil 4 receiving the amplified electrical energy from the in-put tube 1 one connection of the primary winding 24 bein to the plate 10 of the in-put tube 1 and the other connection being to the positive terminal of the B battery 5, while the circuit is completed through the negative terminal 11 of the A battery (not shown).

One terminal of the secondary s 21 of the improved coil 4 is connected b t e conductor 12 to the stator plates 6 o the variable condenser- 3, while the other terminal of the windings 21 is connected to the rotor plates 9 of the variable condenser 3 through the medium of the conductor 13 and the frame 7. The out-put tube 2. is connected through the grid 14 and the conductor 15 with the stator plates 6 of the variable condenser 3, while the circuit from 50 the grid to the filament is completed by a conductor 17 from the negative terminal 16 of the A battery to the rotor plates 9 of the variable condenser 3 through the frame 7.

The description thus far is that of .a conventional type of radio frequency-apparatus, my improvements residing, however, in the from the g The primingl method of winding the radio frequency coil 4. Generally speaking, the improvement consists in arranging the primary windin s 24 relative to the secondary windings 21 in such a manner as to obtain the maximum amount of amplification. It will be noted that the secondary windings 21 are wound upon the insulating tube 18 of the coil 4 in such a manner that the successive convolutions are spaced progressingly from a minimum distance between adjacent convolutions at the end 19 of the coil 4 to av maximum distance at the end 19'. The manner of winding is such as to produce concentrated secondary convolutions at the end 19 of the coil 4 and a comparatively few or widely spaced convolutions at the end 19' of the coil 4. I have shown these successive windings or convolutions of the secondary progressivelyspaced, although it is within the spirit of my invention to provide a minimum inductance per unit length adjacent the area where the primary turns are concentrated in the magnetic field of the secondary, and a maximum inductance per unitlength adjacent that area furthest removed minimum inductance, which latter area is practically independent of the mag netic coupling of the primary turns. whereby the larger portion of the secondary inductance is free to effect oscillations unretarded by the magnetic drag of the primary. windings 24 are thus not wound the 11 length of the tube 18, but

are concentrated as seen in the drawing in' the end 19 andplaced inside of the tube 18, these windings 24 preferably being bankwound. I

The principle of the described arrangement of the primary and secondary windings andthe result obtained are as follows. It is well known that the untuned primary-'24 receives amplified energy from the input tube 1 at a certain wave length, and the magnetic lines of force thereby produced interlace with the convolutions of the secondary windings 21, inducing an electrical potential within these windings 21 and an electrical oscillation in the completed circuit through the variable condenser 3. Now, if the condenser 3 and the coil 4 are tuned to incoming wave lengths, then by the principle of electrical resonance an electrical potential of amplified magnitude is induced across the terminals of the coil 4 and consequently of the condenser induced electrical potential due to resonance of the coil is ex- I pressed in electrical terms, LWI, and that of the condenser by in which L deelectrical potential due to the resonance of I ciency,

properly provide for the system is then impressed upon the grid element 14 of the output tube 2, this grid element as noted being connected by the conductor 15 with the stator plates 6 of the condenser 3. Thus, an increasing amount of electrical energy is then available from the plate element 25 of the tube 2, due to the inner plate-grid action of this tube.

In order to build up a very high value of resonantal potential, LWI,-it is necessary to the coupling factor between the primary windings 24 and the secondary windings 21. If the primary 24 is wound the full length of the secondary 21, then the two magnetic fields interlace uniformly and there is a maximum of electro magnetic drag between the two windings; in other words, the secondary 21 in trying to build up a high magnitude of electrical resonance within itself, is retarded in this action by the interaction of the primary 24. In order to relieve the secondary 21 from this electro magnetic drag and yet have an oscillation imparted to it from the primary 24, I place the latter at one end of the coil 4, preferably the so-called grounded end 19, which is connected to the rotor plates 9 of the condenser 3. By this arrangement, the magnetic lines of force of the primary 24 interlace with only a portion of those of the secondary 21 and relieve the resonantal of a great portion of the primary drag. But in order to impart the proper amount of energy it is advisable to increase the number of turns in the primary 24; In fact, as

shown, I have bank-wound the windings of the primary. In order to enhance these preferred results to a still greater degree of effi- I have wound the secondary 21 with its convolutions at the end 19 of the coils 4 spaced further apart than those convolutions at the end 19, so as to producegreat inductance adjacent the end 19 of the e011 4 and comparatively small inductance adjacent the end 19'. Preferably, I have progressively increased the space between adjacent convolutions of the secondary 21 from the end 19 of the coil 4 to the end 19' where the primary 24 is located. By this arrangement, it will be readily seen that the greatest portion of the inductance of the secondary 1 is concentrated toward the end 19 ofthe e l 4, while at the end 19 this inductance s at a minimum. Consequently, the magnetlc lines of force of the primary 24 interlace with a minimum number of the magnetic lines of force of the secondary 21, and allow the latter to build up its electromotive force of resonance with the minimum of magnetic drag. As stated, it is advisable in this case, in order to pass on a sufiicient amount of electrical energy from the preceding stage of amplification to overcome the electrical resistance of the secondary circuit, to increase the number of turns in the primary and to concentrate the same and this I have done in the manner shown and described.

To efficiently proportion the progressive windings of the secondary 21, and to determine the number of turns in the primary 24, it is necessary to take into consideration the frequency at which the resonance is taking place. electrical resonance of the secondary 21 is an intrinsic property and is not energy passed fromthe primary, although the primary is instrumental in setting up or calling forth this resonance. Therefore, this setting up of the electrical resonance in the secondary by the action of the primary should be accomplished with a minimum amount of drag, and constitutes that energy necessary to overcome the resistance of the secondary. This can be illustrated by an analogy drawn from the action, for instance, of a flat spring, clamped in a vise and positioned in a vertical plane and carrying on its free upper end a suitable weight. By successfully applying a force to such a spring along a hori-' vzontal line of action, it will be set in violent vibration, depending upon the force applied and the manner and place in which and at which it is applied. It is recognized that the vibration will be most easily set up within a given limited area, and that above and below that area, the applied force is less effective. Where the fingers are used to set up the vibration, it will be found that they will exert a minimum drag Within such area, and that the increased vibration will be more efliciently built up within such an area of applied force. The frequency of the system also has a bearing upon the case, and where the weight and spring are so proportioned as to give a high rate of vibration, it will be found necessary to impose the impulses at a point still closer to the clam ed end of the spring in order efficiently to uild up the resonance in the system. Thus, likewise, it is necessary in the design of my improved frequency unit to take into consideration the frequency at which the resonance is taking place in order to properly and most efiiciently space the secondary windings and to determine the number of turns in the primary.

I wish further to point out that the use of my improved radio frequency unit does not require, within certain limits, the use of any so-calledequalizing radio accessories to prevent self-oscillations. Therefore, the

like a hack-saw blade It should be borne in mind that this unit, when properly designed, is simple, noncritical and efficient; The construction permits exceptional facility in selecting and segregating distributing stations on their allocated frequencies.

What I claim is:

1. A coil for use in radio frequency units in which the primary windings are concentrated in one end of the coil and in. which the secondary windings are spaced progressively decreasing distances from the primary winding end to the other end of the coil.

2. A coil for use in radio frequency units in which the primary windings are concentrated in bank condition in one end of the coil and in which the secondary windings are spaced progressively decreasing distances from the primary winding end to the other end of the coil.

3. A coil for use in radio frequency units comprising an insulating support, a secondary wound upon said support with its convolutions more widely spaced upon one portion of the support than they are upon the balance of the support, vand a primary concentrated adjacent the more widely spaced convolutions of the secondar 4. A coil for use in radio f requency units comprising an insulating support, a second ary inductively wound upon said support so as to produce an inductance at one end thereof greater than the inductance at the other end thereof, and a primary concentrated adjacent that end of the support where the secondary inductance is smaller.

5. A- coil for use in radio frequency units comprising an insulating support, a secondary wound upon said support so as to produce an inductance at one end thereof greater than the inductance at the other end thereof, and a primary bankwound within the support at that end thereof where the secondary inductance is smaller.

6. A. coil for use in radio frequency units comprising an insulating support and a secondary winding longitudinally mounted thereon and presenting a comparatively greatdnductance per unit length in one portion thereof and a omparatively small inductance rer unit length in another portion thereof, and aprimary winding concentrated within the last-mentioned portion. 7. radio frequency coil comprising primary and secondary convolutionsin which a section of said secondary is wound toprovide a comparatively great inductance per unit length, and another section thereof wound to provide sparse inductance per unit length, the primary convolutions being magnetically coupled to the secondary convolutions in said sparse section of'inductance.

8. A radio frequency coil comprising bank-wound primary convolutions and secondary convolutions, with a section of said secondary convolutionswound to provide a comparatively great inductance per unit length, and another section thereof wound to provide sparse inductance per unit length,

said bank-wound primary convolutions being magnetically coupled to said secondary convolutions in said sparse section of inductance.

Signed by me this 10th day of Jan. 1927.

THEODORE E. FRIEND. 

